The goal of this application is to enable Dr. Leuchter's to undertake a new research program focused on cognitive neurophysiology in the elderly. Dr. Leuchter proposes to develop new skills in : 1) the use of cognitive tasks for cerebral activation; 2) the recording of neurophysiologic data during task performance; and 3) the study of cognitive changes in aging. He has selected a panel of expert consultants who will work with him to develop these skills. With the support of this Award, Dr. Leuchter will utilize his quantitative electroencephalography (QEEG) and magnetic resonance imaging (MRI) methods to examine differences in cognition between young and old adults, and to study the cognitive decline that accompanies aging. He will test the following three general hypotheses: 1. Differences in cognition between young and elderly subjects will be reflected in differences in cerebral activation and inhibition accompanying cognitive tasks: 2. Elderly subjects with deep white-matter lesions are at greater risk for cognitive dysfunction than those without these lesions; and 3. Elderly subjects with poor performance on cognitive tasks, who have white-matter lesions that affect the brain systems showing poor performance, will be at greater risk for progressive or global impairment than those without such lesions. Dr. Leuchter has developed enhanced QEEG methods that may provide more information about cerebral activation during tasks than previously possible. He will use these methods in this revised research plan to study 50 young and 100 elderly adults with QEEG during the performance of a battery of cognitive tasks. Some of the elderly subjects will have risk factors for the development of white- matter lesions. Quantitative MRI will be used both the locate recording electrodes in relation to the brain, and to determine the volume of white-matter disease. All subjects will be examined with a neuropsychological test battery, task-activated QEEG, and MRI at entry into the study and at three years. Comparisons will be performed between young and old subjects, and with groups of elderly subjects, to determine if deficient task activation is associated with poorer performance and/or cognitive decline.